Kestrel gRPC support: provide more efficient APIs for reading request and response bodies

[jtattermusch]

One of the possible ways how to integrate with gRPC is to write a generic handler that reads http request's body (httpContext.Request.Body) and parses them into grpc request messages and writes grpc response messages into httpContext.Response.Body. This works pretty well (see prototype in https://github.com/jtattermusch/grpc-aspnetcore-experiments), but both request body and response body are instances of System.IO.Stream, which works but isn't particularly efficient (e.g. copying of the data is required, it's hard to use with memory pooling etc.) and will probably become a performance bottleneck in the future.
Is there a way to access request and response bodies e.g. in terms of the new System.IO.Pipelines API?

Context: grpc/grpc#15139

[muratg]

cc @davidfowl

[davidfowl]

Yes, there are plans to get this done for ASP.NET Core 3.0.

[Tratcher]

In addition to making the pipes available we'll also need to make every middleware that wraps the body at least partially pipes aware. E.g. Anything that wraps the body must also wrap the pipe, or replace one or the other with a redirector. See Response Compression, Response Caching, etc.. This is similar to how they handle or redirect ISendFileFeature today.

[davidfowl]

Yes, this is a know design challenge.

[JunTaoLuo]

I think @jkotalik is actively involved with this work. Please reassign if that's not the case.

[jkotalik]

The base layer for this is done with #7603 and #7110. Counting this as done.